sedimentary

Chert (with Quartz Vein)

Microcrystalline silica (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Brown, tan, and gray with white veining; Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Hardness: 7 on Mohs scale
Color: Brown, tan, and gray with white veining
Luster: Dull to waxy

Identified May 3, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale; Color: Brown, tan, and gray with white veining; Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Formation & geological history

Formed through the accumulation of siliceous remains of organisms or chemical precipitation from silica-rich fluids in sedimentary basins. The white vein suggests secondary quartz precipitation in a fracture.

Uses & applications

Historically used for making stone tools (arrowheads). Modernly used in landscaping, road construction, and as a collector specimen when featuring interesting patterns.

Geological facts

Chert is so hard it can scratch steel. It is one of the most durable rocks and is often found as rounded cobbles in riverbeds or beaches because it resists weathering better than surrounding rocks.

Field identification & locations

Identify by its waxy texture, conchoidal (shell-like) fractures, and its ability to scratch glass. Commonly found in limestone or chalk deposits and along coastlines.